 He gained a reputation for his role in defending Finland and Estonia from Anglo-French invasion during the Crimean War and was also crucial in suppressing and crushing the Polish January Uprising of 1863, during which rebel forces carried out numerous failed assassination attempts on him, martial law was consequently declared in Poland.Berg also held responsible for improving the economy and industry of Finland and Poland during his time as viceroy.As a German, Berg was never keen of the Russification policies introduced in Poland, being opposed to the Pan-Slavism idealogy of the Russians and keen towards the foreign policies of Germany.